Consensus among Physiotherapists in the United Kingdom on the Use of Normal Saline Instillation Prior to Endotracheal Suction: A Delphi Study (2025)

ABSTRACT

Purpose: To investigate whether physiotherapists consider normal saline instillation (NSI) useful before endotracheal suctioning and, if so, when.

Methods: Sixty-eight respiratory physiotherapists recruited from the United Kingdom's Association of Chartered Physiotherapists in Respiratory Care agreed to participate in a Delphi study. Clinicians' opinion of when NSI should be used was established and developed into statements. Level of agreement with each statement was collated through three rounds of a questionnaire. Clinicians' experiences were also reported.

Results: From the 52 responses to the third questionnaire, there was consensus that respiratory physiotherapists in the United Kingdom would use NSI when sputum retention is a problem, particularly when treatment options are limited (96%) and when sputum is obstructing the airway (92%). They agreed that non-bronchoscopic bronchoalveolar lavage can be used to resolve persistent atelectasis (70%). They would not use NSI for a test treatment during initial assessment without evidence of retained secretions (94%), when secretions are copious but can be cleared by alternative physiotherapy techniques (96%), to enhance a cough unless very strong evidence indicates retained secretions (81%), or to compensate for inadequate suction technique (90%).

Conclusion: This study provides clinicians' views about when NSI could be used.

INTRODUCTION

Normal saline instillation (NSI) is the process of instilling saline directly down a patient's endotracheal (ET) or tracheostomy tube prior to endotracheal suction. A syringe at the mouth of the ET/tracheostomy tube can be used, or, alternatively, a sterile vial of saline can be connected to the designated port on a closed suction system and saline washed down the catheter. The proposed advantages of NSI are loosening of thick secretions, enhanced cough, increased secretion mobilization and clearance, dilution of secretions, and lubrication of the suction catheter.¹ Of these, only enhanced secretion clearance has been investigated and supported.^2,3

Studies investigating the effect of NSI on outcomes such as oxygen saturation, oxygen consumption, and risk of infection suggest that it may be detrimental.^4–9 These studies, however, focused on samples in which a sputum problem was unlikely because of the brief period the subjects were likely to have been ventilated.^4–6,9 Some studies also had methodological flaws and lacked adequate detail, calling into question the validity and reliability of their results. Ackerman⁴ and Ackerman and Mick⁵ failed to detail whether pre-oxygenation, advised by authors such as Oh and Seo,¹⁰ was undertaken before suction. This lack of detail with respect to suction procedure leads to questions about the authors' reported reduction in saturations, as this could be due to variations in practice (pre-oxygenation or not) rather than to NSI. Hagler and Traver stated that NSI is an infection risk but did not consider that some bacteria washed off an ET/tracheostomy tube by NSI are likely to be removed by the subsequent suction procedure.⁷ Study results may also be statistically but not clinically significant. For example, a 2% drop in saturations could be a drop from 100% to 98%.^7,8 Such limitations result in low-quality evidence that is of limited clinical value.

Surveys have indicated that NSI has been used extensively with patients requiring suction;^11–13 39% of physiotherapists and 43% of respiratory therapists in Canada have reported using it routinely, and 46% and 51% respectively have reported using it sometimes.¹⁴ Despite this, two groups have recommended banning NSI.^15,16 However, this recommendation is based on a misrepresentation of the work of Ackerman and Mick, who actually suggested that routine use of NSI is not supported.⁵ Canadian guidelines produced by Brooks et al.¹⁷ indicate that there is currently no evidence to support or refute the use of NSI; more recently, Celik and Kanan have reiterated the view that NSI should not be used routinely,¹⁸ suggesting that NSI should be used only when it is needed and when the patient's response to it has been established.

Within the United Kingdom, anecdotal reports have indicated that some hospitals incorporated the complete ban of NSI in their nursing suction protocols, based on reviews reported in nursing literature, and that physiotherapists, despite being autonomous practitioners, are being encouraged to comply.^15,16 This is particularly pertinent if it is considered that sputum retention, one of the key reasons for using NSI,¹ could itself be detrimental to oxygenation. It is possible that the potential of ultimately improving oxygenation by removing secretions with NSI could reduce the importance of any possible detrimental effects. If secretions cannot be removed with other physiotherapy techniques, the ban on NSI could potentially be detrimental to patient care. Given this contradiction in recommendations, it is important to establish whether physiotherapists believe that NSI should be used and, if so, under what circumstances. Sackett et al. believe that clinicians' experience can contribute to informing evidence-based practice if research is lacking.¹⁹ Therefore, clinicians' expert opinion can provide evidence for physiotherapists' practice regarding the use of NSI, albeit at a lower level than the evidence produced by randomized controlled trials,¹⁹ and can also provide direction for further studies to establish whether NSI has a role prior to suctioning.

The purpose of this study was to identify whether physiotherapists working in intensive care environments consider NSI to be useful and, if so, in what situations. Their views and experiences can provide an alternative source of evidence.

METHOD

RESULTS

Of the initial 86 physiotherapists identified, 68 returned questionnaires (a 79% response rate). Of these, 62 agreed to participate in future rounds, and 95% (n = 59) completed Round 2. One additional response was excluded because it was received after the results had been collated. In Round 3, 60 questionnaires were sent out and 52 returned (an 87% response rate). In all, 76% of the initial 68 respondents to Round 1 completed the study.

Ninety-four percent of participants were experienced clinicians, that is, Senior I or above (see Table 1), and 83% worked in intensive care weekly or more often (see Table 1). Table 2 shows the number of respondents at each grade for each round of the study.

In Round 1, question 3 asked clinicians whether or not they would consider using NSI. There was 100% agreement that NSI would be considered in certain situations. Results of Round 2 served only to inform Round 3 and are not presented here. The percentage response for statements relating to nature of secretions, sputum retention, and airway and suction issues are shown in Table 3. Only levels of agreement or disagreement are shown; levels of “no opinion” were very low—less than 6% for all statements except 3(i) (10%), 10 (12%), and 11(ii) (9%)—and therefore are not reported.

There was 100% agreement that systemic hydration and humidification should be maximized if secretions are thick or tenacious, particularly if they are not clearing with available treatment techniques. All other statements (see Table 3) show a high level of agreement (> 70%), indicating consensus for each statement. The use of NSI when secretions are thick or obstructing a bronchus or airway (statements 1, 4, and 5 in Table 3) was supported by the clinicians' reported experiences (see Box 1).

Although respondents in earlier rounds referred specifically to patients with inhalation burns, a large number of respondents had no experience of or no opinion on this issue (see Figure 3). Statements become progressively more specific with respect to the situations in which NSI can be used, and the level of “no experience” for each statement was constant at 45%. With the “no experience group excluded from the calculation, agreement was reached on NSI use when burn-injured patients have thick/tenacious secretions that are not clearing with other techniques (71% agreement) and “if the secretions are impairing or likely to impair ventilatory status” (75% agreement).

DISCUSSION

These results represent the opinions of a relatively small sample of clinicians, but their level of experience and the frequency with which they worked in ICU suggest that they have extensive and relevant experience. Although 16 respondents were lost during the study, the level of experience and frequency of ICU work was consistent through all three rounds, enhancing the reliability of the results.²² Loss of respondents may indicate response fatigue. While this could be seen as a threat to validity, the high agreement level required for consensus would indicate strong support for the statements and, if achieved, would improve validity.²³

In previous studies, agreement levels between 51% and 80% have been used to indicate consensus.^22,24 The relatively high level of agreement chosen for the present study (70%) improves validity, but it is an arbitrary number. There are wide variations in how the Delphi technique is undertaken, due to lack of universal guidelines, and these variations are mirrored in the ways consensus is demonstrated.²⁵

The participants' agreement that they would use NSI if secretions are thick or tenacious, if secretions are adversely affecting or are likely to adversely affect ventilatory status, and if other available treatment techniques are not clearing the secretions is supported by Schwenker et al.²⁶ This complex statement was developed from specific statements provided by clinicians, who did not differentiate between “thick” and “tenacious” or provide definitions for these terms. A degree of clarification is provided through the clinicians' descriptions of their experiences (see Box 1), which make reference to secretions on the outside of the catheter or occluding the airway and which link to the definition provided by Druding: “secretions are adhering to the ETT or suction catheter, mucous is obstructing the airway.”^27(p.212) However, unlike Druding, who advocates NSI if a suction catheter is not eliciting an acceptable cough, respondents in this study indicated that this is acceptable only if secretions are likely to cause a problem.²⁷

Many of the statements made by respondents in this study were qualified by “available treatment techniques,” a term that was not described or defined. Treatment techniques commonly used in ICU are manual hyperinflation, vibration, shaking, and percussion. Techniques available to physiotherapists, however, are determined by the patient's medical condition, the expertise of the clinician, and the available resources, and will therefore vary among patients.

Only five statements had less than 80% agreement, but these still achieved consensus, since results were above the 70% level required. The first relates to the use of non-bronchoscopic bronchoalveolar lavage (NB-BAL); it shows that this group did not agree that NB-BAL could be used to resolve atelectasis caused by mucous plugging and unresponsive to other treatment options. However, the number of respondents claiming to have no experience with this technique was high, and when this group was excluded from the calculation, there was agreement that NSI could be useful.

NB-BAL has been used in three studies of paediatric populations; despite minor variations in technique, all three identified successful resolution of refractory atelectasis.^28–30 No literature was found relating to NB-BAL in adults; however, the development of collateral ventilation, which occurs between childhood and adulthood, could allow saline to pass behind the plug, enhancing the technique's effect in adults. Work by Hanley et al. suggests that this would not be possible, because the saline does not reach beyond the main stem bronchus.³¹ However, their study involved instilling saline via a syringe at the top of the endotracheal tube, a different method from instillation down a narrow-bore tube wedged at the carina, as used in NB-BAL; it is not possible to assume that saline would reach the same point in the lungs. In addition, they reported only seven cases (five dogs and two humans), and generalization from one small, mixed sample should be undertaken with caution.³¹

The next statement that demonstrated significant results with an agreement level below 80% related to the use of NSI to help clear secretions obstructing the airway. Although clinicians agreed that using NSI to clear an ET or tracheostomy tube could result in complete occlusion, necessitating re-intubation, they also agreed that NSI can at times be useful in these situations for clearing the secretions causing the occlusion.

For patients with inhalation burns, agreement was reached only when calculated without the “no experience” group, and then only for situations similar to other patients (i.e., when secretions are thick/tenacious, are not clearing with other techniques, and are impairing or likely to impair ventilatory status). The number of respondents reporting “no experience” for these three statements suggests that only those with experience changed their views as the statements in the questionnaire became more specific.

The level of agreement for inhalation burns may differ from that for sputum retention because some clinicians who reported having no opinion (a proportion that changed across the three statements relating to inhalation burns; see Figure 3) may have based their opinions on theory rather than on clinical experience. There is a lack of literature either supporting or refuting NSI use in the situations identified. However, the progressive and systematic approach described in the clinicians' reported experiences (see Box 1) provides support for aspects such as the use of NSI for retained secretions and mucous plugging causing airway occlusion. This increases the reliability and validity of the results, as these incidents represent specific reported examples of the situations mentioned in the questionnaire.

CONCLUSIONS

The results of the present study document the opinions of a group of specialist respiratory physiotherapists on situations when NSI would be appropriate to use. These situations are as follows: when sputum retention due to thick or tenacious secretions is affecting, or is likely to affect, ventilatory status and “available treatment techniques” are not clearing the secretions; when atelectasis due to mucous plugging occurs and “available techniques” are unable to clear it; and when ETT/tracheostomy obstruction or partial obstruction due to sputum occurs. In addition, the technique of NB-BAL can be used to resolve persistent atelectasis. Conversely, the respondents agreed that NSI should not be used for a test treatment during initial assessment, unless there is very strong evidence to indicate retained secretions, or when secretions are copious but can be cleared by alternative physiotherapy techniques. NSI is also not appropriate to enhance a cough, unless there is very strong evidence to indicate retained secretions, or to compensate for inadequate suction technique.

KEY MESSAGES

ACKNOWLEDGEMENT

Thanks to Dr. Sue Barnard and Mrs. E. Hancock for their guidance in the development of this paper.

Roberts FE. Consensus among physiotherapists in the United Kingdom on the use of normal saline instillation prior to endotracheal suction: a Delphi study. Physiother Can. 2009; 61:107-115.

REFERENCES